There is an increasing interest in using Underwater Acoustic Sensor Networks (UASNs) for various oceanographic applications, such as pollution monitoring, seismic monitoring, environmental data collection, offshore exploration, and tactical surveillance. UASNs rely on acoustic communications; however, the underwater acoustic channel is highly variable and its link quality depends on environmental factors and the locations of the communicating nodes. Therefore, ensuring reliable communication in UASNs is quite difficult. Moreover, path losses and retransmissions lead to the wastage of energy resources and reduce the network lifetime. In this study, we have utilized wellknown underwater modulation schemes to analyse and simulate various underwater scenarios with different depth, distance and Bit Error Rate (BER) values in order to make a fair comparison between the modulation schemes and obtain the optimal transmission power. Performance evaluations show that 32-PSK and 16-QAM techniques achieve the minimum energy consumption rates and enhance network lifetime.